Disclosed is the use of an anti-Bv8 antagonist antibody or functional fragment thereof in the manufacture of a medicament for treating an anti-VEGF resistant tumour. Further disclosed is a method for identifying an anti-VEGF resistant tumour-bearing human subject for treatment with an anti-Bv8 antagonist antibody or functional fragment thereof, comprising determining in a sample obtained from the subject, that the subject is refractory to treatment with a VEGF antagonist.
